SOLUTION: The measure of the vertex angle of an isosceles triangle is 50 degrees. Find the measure of an exterior angle to one of the base angles of the triangle. These are the choice

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Question 878669: The measure of the vertex angle of an isosceles triangle is 50 degrees. Find the measure of an exterior angle to one of the base angles of the triangle.

These are the choices given in my math book.
(A) 65 degrees
(B) 125 degrees
(C) 115 degrees
(D) 80 degrees
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Let x = the measure of the base angle


There are two congruent base angles in the isosceles triangle. The 3 angles of the triangle must add to 180 degrees. This means, x%2Bx%2B50=180, solve for x to get


x%2Bx%2B50=180


2x%2B50=180


2x=180-50


2x=130


x=130%2F2


x=65


So the base angle is 65 degrees. This is an interior angle. We want an exterior angle. So if y is an exterior angle to the 65 degree angle, then


y%2B65=180


y=180-65


y=115


Making the final answer (C) 115 degrees